Vehicles may be adorned or outfitted with aftermarket accessories to improve the look or utility of a vehicle. For example, an accessory such as lighting may be available from manufacturers in the form of a light-bar comprised of multiple light units, attached to or within, a housing that is mountable to the vehicle body, or individual lighting units that must be separately mounted to the vehicle body. Mounting lighting as described however, requires alteration of the vehicle body, which can void warranties, be difficult for most vehicle owners, or be cost prohibitive if the vehicle owner chooses to pay a third party installer to attach the lighting accessory. Further adding to the difficulty is the differing dimensions of accessories and the associated mounting hardware and/or requirements of the accessories from different manufactures. Accordingly, there is a need for an improved accessory mount structure or system that accommodates many alternately designed and dimensioned aftermarket accessories and the associated mounting requirements.